Abstract:  In order to estimate the 3D fragmentation distribution of rock blocks， the method of calculating the 3D sieve dimensions based on the 2D graphics obtained by image segmentation of the rock blocks was studied. The blocks were classified by the 3D shape parameters ε and κ， and the equivalent size of the block is calculated as the sieve block size according to the classification result. The collection of 3D rock block models was established by using the discontinuity network simulation. Then the block models were cut by a set of planes to obtain the 2D contours corresponding to the rock blocks. The 2D and 3D geometric parameter values of the blocks according to the 2D contours and the 3D models of the rock blocks. Thus， the relationship between 2D and 3D geometric parameters was established by statistical analysis and regression analysis. The formula for calculating the sieve dimensions of rock blocks by 2D geometric parameters was derived， and a quantitative distribution of mineral rock blocks was obtained. The experimental comparison showed that the distribution of sieve block size calculated according to 2D geometric parameters were consistent with the actual sieve block size of the 3D rock models.

Key words: Fragmentation distribution, Equivalent size, Discontinuity network, Block shape classification